diff -ur grub-2.02.orig/util/grub.d/00_header.in grub-2.02/util/grub.d/00_header.in

--- grub-2.02.orig/util/grub.d/00_header.in	2017-12-02 12:21:57.000000000 +0300

+++ grub-2.02/util/grub.d/00_header.in	2017-12-02 12:27:09.380748033 +0300

@@ -325,6 +325,10 @@

     fi

     cat << EOF

 fi

+# interrupt grub booting process if shift key pressed

+if keystatus --shift;then

+  set timeout=-1

+fi

 EOF

 }